In an ordinary screw vice one has solved the problem by a simple instalment of a work piece between two jaws. Usually one of the jaws is fixed and one is movable through some kind of guided operation, that leads to a clamping of the piece between the jaws.
The problem now is to arrange a number of fixed double acting screw vices on a working table or jig so that location of the fixed jaws will be described in a way, that the orientation can be used as coordinates in a numerically controlled machine, which will become reproducible when mounted in the machine.